HIRES TOI-1136s planets and planet b radial velocities

The well-aligned planetary system and the lack of a detected binary companion together suggest that TOI-1136's resonant chain formed in an isolated, quiescent disk with no stellar flyby, disk warp, or significant axial asymmetry. With period ratios near 3:2, 2:1, 3:2, 7:5, and 3:2, TOI-1136 is the first known resonant chain involving a second-order MMR (7:5) between two first-order MMRs. The formation of the delicate 7:5 resonance places strong constraints on the system's migration history.

Short-scale (starting from ~0.1au) Type-I migration with an inner disk edge is most consistent with the formation of TOI-1136. A low disk surface density ({Sigma}1au<~103g/cm^2^; lower than the minimum-mass solar nebula) and the resultant slower migration rate likely facilitated the formation of the 7:5 second-order MMR.